Carbohydrates ingested by a mammal are initially digested (hydrolyzed) to some extent with salivary α-amylase in the mouth and stomach, and then digested wholly with pancreatic α-amylase in the duodenum and jejunum into an oligosaccharide or disaccharide. There are further hydrolyzed by glucoside-hydrases such as glucoamylase and maltase to finally become a monosaccharide such as glucose, which is absorbed up through the villi on the intestinal tract membranes. Thus, after ingestion of carbohydrates, there takes place a temporary rise of blood glucose level, or so-called hyperglycemia, due to the absorption of glucose. Normally, however, this temporarily elevated blood glucose level is adjusted to stay in a normal range by the homeostasis maintenance system in the living body to recover from hyperglycemia.
However, abnormalities of carbohydrate metabolism, such as long-time continuance of alimentary hyperglycemic symptoms or occurrence of an abnormally high blood glucose level, may lead to a disease called hyperglycemia, causing such cases as obesity and diabetes. This obesity is caused as secretion of a large volume of insulin is promoted by a hyperglycemic symptom induced by overeating, provoking an increase of synthesis of fat and a decrease of its decomposition to accumulate fat in the body. On the other hand, diabetes is caused as secretion of a large volume of insulin is promoted by a hyperglycemic symptom induced by overeating to provoke a reduction of sensitivity of insulin receptors or exhaustion of β cells of the islet of Langerhans in the pancreas. It is also known that obesity and diabetes tend to trigger many serious complications such as hyperlipidemia, hypertension, arteriosclerosis, autonomic troubles and cataract.
As the potent therapeutic agents for such hyperglycemia, there are clinically used the pharmaceuticals containing a digestive enzyme inhibitor, such as “Basen” containing Voglibose (produced by Takeda Pharmaceutical Industries Co., Ltd.) and “Glucobay” containing acarbose (produced by Bayer Ltd.). Both of these compounds, however, have the disadvantage of producing undesirable side effects, such as causing abdominal distention, meteorism, increased flatulence, loose passage, diarrhea or abdominal pain.